The invention relates to a geometrical or optical measuring instrument, and more particularly to a portable instrument which combines an electronic distance or range finder with an electronic difference finder for vertical (i.e., elevational) angle mensuration.
It is an object of the invention to provide an apparatus that can determine a vertical clearance between a bridge overpass and an under-passing highway from a remote distance away.
It is an alternate object of the invention that the above apparatus be portable in the sense that it can be mounted to and operated from a vehicle, or else in some versions of the invention be handheld.
It is another object of the invention that the above invention be sighted manually on at least one of the bridge overpass or the under-passing highway, but otherwise instantaneously give computed values after switched ON or the like.
A number of additional features and objects will be apparent in connection with the following discussion of preferred embodiments and examples.